The Ubuntu-specific "selinux" and "selinux-policy-ubuntu" packages documented here have not received much attention since Karmic, and appear to be effectively broken in Precise.

If you wish to use SELinux in Ubuntu, the "selinux-basics" and "selinux-policy-default" packages from Debian are still being actively maintained. Documentation relevant to those packages can be found at http://wiki.debian.org/SELinux